LangChain Install & Auth

Overview

Set up LangChain SDK and configure LLM provider authentication credentials.

Prerequisites

• Python 3.9+ or Node.js 18+
• Package manager (pip, poetry, or npm)
• LLM provider account (OpenAI, Anthropic, Google, etc.)
• API key from your LLM provider dashboard

Instructions

Step 1: Install LangChain Core

# Python (recommended)
pip install langchain langchain-core langchain-community

# Or with specific providers
pip install langchain-openai langchain-anthropic langchain-google-genai

# Node.js
npm install langchain @langchain/core @langchain/community

Step 2: Configure Authentication

# OpenAI
export OPENAI_API_KEY="your-openai-key"

# Anthropic
export ANTHROPIC_API_KEY="your-anthropic-key"

# Google
export GOOGLE_API_KEY="your-google-key"

# Or create .env file
echo 'OPENAI_API_KEY=your-openai-key' >> .env

Step 3: Verify Connection

from langchain_openai import ChatOpenAI

llm = ChatOpenAI(model="gpt-4o-mini")
response = llm.invoke("Say hello!")
print(response.content)

Output

• Installed LangChain packages in virtual environment
• Environment variables or .env file with API keys
• Successful connection verification output

Error Handling

| Error | Cause | Solution | |-------|-------|----------| | Invalid API Key | Incorrect or expired key | Verify key in provider dashboard | | Rate Limited | Exceeded quota | Check quota limits, implement backoff | | Network Error | Firewall blocking | Ensure outbound HTTPS allowed | | Module Not Found | Installation failed | Run pip install again, check Python version | | Provider Error | Service unavailable | Check provider status page |

Examples

Python Setup (OpenAI)

import os
from langchain_openai import ChatOpenAI

# Ensure API key is set
assert os.environ.get("OPENAI_API_KEY"), "Set OPENAI_API_KEY"

llm = ChatOpenAI(
    model="gpt-4o-mini",
    temperature=0.7,
    max_tokens=1000
)

Python Setup (Anthropic)

from langchain_anthropic import ChatAnthropic

llm = ChatAnthropic(
    model="claude-3-5-sonnet-20241022",
    temperature=0.7
)

TypeScript Setup

import { ChatOpenAI } from "@langchain/openai";

const llm = new ChatOpenAI({
  modelName: "gpt-4o-mini",
  temperature: 0.7
});

Resources

• LangChain Documentation
• LangChain JS/TS
• OpenAI API Keys
• Anthropic Console

Next Steps

After successful auth, proceed to langchain-hello-world for your first chain.